Abstract

These numerical studies show that ionization influences both the
transport and dynamical properties of compressible convection near the
surface of the Sun. About two-thirds of the enthalpy transported by
convective motions in the region of partial hydrogen ionization is
carried as latent heat. The role of fast downflow plumes in total
convective transport is substantially elevated by this contribution.
Instability of the thermal boundary layer is strongly enhanced by
temperature sensitive variations in the radiative properties of the
fluid, and this provides a mechanism for plume initiation and cell
fragmentation in the surface layers. As the plumes descend, temperature
fluctuations and associated buoyancy forces are maintained because of
the increased specific heat of the partially ionized material. This can
result is supersonic vertical flows. At greater depths, ionization
effects diminish, and the plumes are decelerated by significant
entrainment of surrounding fluid.

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